Cream the icing sugar and butter together until the mixture becomes light and fluffy. Add the vanilla, cake flour, cornflour and food colouring, mixing to become a rough dough. Shape the dough into equal sized balls and place on a greased baking tray. Press down gently with a fork creating that signature melting moment print. Place the cookies in an oven preheated to 180C to make for 15 minutes or until the cookie becomes slightly firm and holds its shape well, remove it from the oven to cool and firm further. Once completely cool sandwich 2 of the cookies together with the custard icing and serve